Conveying means and method

ABSTRACT

Apparatus for providing linear motion to a generally flat flexible material, comprising: (a) at least one piezoelectric ceramic motor situated on a first side of the flat flexible material and having a contact surface which contacts the flat flexible material and which imparts said linear motion; and (b) a bearing surface situated on a second side of the flat flexible material opposite said contact surface.

RELATED APPLICATIONS

The present application is a U.S. national application ofPCT/IL97/00410, filed Dec. 15, 1997.

FIELD OF THE INVENTION

The present invention relates to linear motion and to piezoelectricmotors generally and more particularly to the use of piezoelectricmotors for moving delicate materials, such as paper.

BACKGROUND OF THE INVENTION

Linear motion and piezoelectric motors are known in the art. SU 693493describes a piezoelectric motor comprising a flat rectangularpiezoelectric plate having one electrode covering essentially all of onelarge face of the plate (“the back face”) and four electrodes eachcovering a quadrant of the front face. The back electrode is groundedand the electrodes of the front face are electrically connected on thediagonal. Two ceramic pads are attached to one of the long edges of theplate and these pads are pressed against the object to be moved by aspring mechanism which presses the other long edge.

The long and short edges of the piezoelectric ceramic have similarresonant frequencies (for different mode orders) such that, when onepair of connected electrodes is excited with an alternating current (AC)voltage to which the ceramic is responsive, the object moves in onedirection, and when the other pair of electrodes is excited, the objectmoves in the other direction.

SUMMARY OF THE PRESENT INVENTION

One aspect of the present invention is concerned with the transport offlexible materials such as paper and cloth.

In a preferred embodiment of the invention a piezoelectric motor is usedto move the material.

There is thus provided, in accordance with a preferred embodiment of theinvention, apparatus for providing linear motion to a generally flatflexible material, comprising:

(a) at least one piezoelectric ceramic motor situated on a first side ofthe flat flexible material and having a contact surface which contactsthe flat flexible material and which imparts said linear motion; and

(b) a bearing surface situated on a second side of the flat flexiblematerial opposite said contact surface.

In one preferred embodiment of the invention the bearing surface is thesurface of a roller. In other preferred embodiments of the invention,the bearing surface is a contact surface associated with a secondpiezoelectric motor.

In these other preferred embodiments of the invention, the bearingsurface is a contact surface of a second piezoelectric motor and thesecond piezoelectric motor also imparts said linear motion to the flatflexible material via said contact surface, preferably the at least oneand the second piezoelectric motors both impart linear motion to theflexible material in the same direction.

In one of these other preferred embodiments of the invention, the atleast one and second piezoelectric motors impart said linear motion in agiven direction during motion periods which alternate with periodsduring which said motion is not applied and the motion periods of the atleast one and the second piezoelectric motors at least partiallyoverlap. Preferably, the motion periods of one of the at least one andthe second piezoelectric motors is fully contained within the motionperiod of the other piezoelectric motor. Preferably, the motion periodsof the at least one and the second piezoelectric motors coincide.

Preferably, the contact surfaces of the at least one piezoelectric motorand the second piezoelectric motor are displaced toward the flexiblematerial during their respective periods of motion such that thematerial is pinched between the respective contact surfaces.

Alternatively the contact surface of the at least one piezoelectricmotor is displaced toward the flexible material during the period ofmotion of the at least one piezoelectric motor and wherein the contactsurface of the second piezoelectric motor is displaced away from theflexible material during the period of motion of the at least onepiezoelectric motor. Preferably, the contact surface of the secondpiezoelectric motor is displaced toward the flexible material during theperiod of motion of the second piezoelectric motor and the contactsurface of the at least one piezoelectric motor is displaced away fromthe flexible material during the period of motion of the secondpiezoelectric motor, such that the at least one piezoelectric motor andsecond piezoelectric motor alternately apply motion to the flexiblematerial. While it might be expected that this apparatus would notoperate since the flexible material would move from side to side,remaining in contact with both motors and thus not moving at all.However, it appears that even the relatively low mass and stiffness ofpaper is sufficient to allow for the motors to independently move thematerial.

In a preferred embodiment of the invention, the at least onepiezoelectric motor comprises:

a second contact surface which contacts and is operative to apply linearmotion to a second portion of the flexible material;

and further comprising:

a second bearing surface situated on a second side of the flat flexiblematerial opposite said second contact surface.

As with the first bearing surface, the second bearing surface may be aroller or a contact surface of an additional piezoelectric motor. Theadditional piezoelectric motor preferably cooperates with the secondcontact surface in the same way as the second piezoelectric motorcooperates with the contact surface.

There is further provided, in accordance with a preferred embodiment ofthe invention, a method for providing linear motion to a generally flatflexible material, comprising:

(a) contacting a contact surface of at least one piezoelectric ceramicmotor with a first side of the flat flexible material, said at least onemotor being operative to impart linear motion to surfaces which are incontact with the contact surface; and

(b) providing a bearing surface on a second side of the flat flexiblematerial opposite said contact surface.

In one preferred embodiment of the invention the bearing surface is thesurface of a roller. In other preferred embodiments of the invention,the bearing surface is a surface associated with another piezoelectricmotor.

In these other preferred embodiments of the invention, the bearingsurface is a contact surface of a second piezoelectric motor and whereinthe second piezoelectric motor also imparts said linear motion to theflat flexible material via said contact surface, preferably the at leastone and the second piezoelectric motors both impart linear motion to theflexible material in the same direction.

In one of these other preferred embodiments of the invention, the atleast one piezoelectric motor and the second piezoelectric motor impartsaid linear motion in a given direction during motion periods whichalternate with periods during which said motion is not applied and themotion periods of the at least one piezoelectric motor and the secondpiezoelectric motor at least partially overlap. Preferably, the motionperiods of the at least one piezoelectric motor and the secondpiezoelectric motor is fully contained within the motion period of theother piezoelectric motor. Preferably, the motion periods of the atleast one piezoelectric motor and the second piezoelectric motorcoincide.

Preferably, the contact surfaces of the at least one piezoelectric motorand the second piezoelectric motor are displaced toward the flexiblematerial during their respective periods of motion such that thematerial is pinched between the respective contact surfaces.

Alternatively the contact surface of the at least one piezoelectricmotor is displaced toward the flexible material during the period ofmotion of the at least one piezoelectric motor and wherein the contactsurface of the second piezoelectric motor is displaced away from theflexible material during the period of motion of the at least onepiezoelectric motor. Preferably, the contact surface of the secondpiezoelectric motor is displaced toward the flexible material during theperiod of motion of the second piezoelectric motor and wherein thecontact surface of the at least one piezoelectric motor is displacedaway from the flexible material during the period of motion of thesecond piezoelectric motor, such that the at least one piezoelectricmotor and the second motor alternately apply motion to the flexiblematerial.

In a preferred embodiment of the invention the method includes:

(a) contacting a second contact surface of the at least onepiezoelectric ceramic motor with a first side of the flat flexiblematerial, said motor being operative to impart linear motion to surfaceswhich are in contact with the second contact surface; and

(b) providing a second bearing surface on a second side of the flatflexible material opposite said second contact surface.

As with the first bearing surface, the second bearing surface may be aroller or a contact surface of an additional piezoelectric motor. Theadditional piezoelectric motor preferably cooperates with the secondcontact surface in the same way as the second piezoelectric motorcooperates with the contact surface.

Additionally, in accordance with a preferred embodiment of the presentinvention, the piezoelectric ceramic motor has two upper and two lowerelectrodes and wherein the two upper electrodes are of the same size butdifferent than the size of the two lower electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description taken in conjunction with thedrawings in which:

FIG. 1 is a schematic illustration of apparatus for providing linearmotion for a flat flexible material, constructed and operative inaccordance with a first embodiment of the present invention;

FIG. 2 is an enlarged elevational detail of the apparatus of FIG. 1;

FIG. 3 is a schematic illustration of a second embodiment of the presentinvention in which a single piezoelectric motor and a pair of rollerdevices are used in combination for providing horizontal linear motion;

FIG. 4 is a schematic illustration of a third embodiment of the presentinvention in which a piezoelectric motor is configured to providedifferential movement of the material to be moved;

FIG. 5 is a schematic illustration of apparatus for providing linearmotion to two individual lines of flat flexible material, constructedand operative in accordance with a fourth embodiment of the invention;and

FIG. 6 is a schematic illustration of a fifth embodiment of the presentinvention in which a three piezoelectric motors provide horizontallinear motion.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1 which illustrates apparatus 10 forproviding linear motion for a delicate material 12, constructed andoperative in accordance with a first embodiment of the presentinvention.

Apparatus 10 comprises upper and lower piezoelectric motor units 14A and14B, respectively, located along a vertical line, on two opposing sidesof delicate material 12. Delicate material 12 is any relatively softmaterial, which is fragile and flexible, such as paper or cloth. Thepiezoelectric motor units, generally designated 14, are connected to apower source 15.

Upper and lower piezoelectric motor units 14A and 14B have similarelements and thus similar reference numerals are used throughout. Thesuffix “A” refers to the upper piezoelectric motor unit 14A and thesuffix “B” refers to the lower piezoelectric motor unit 14A.

The piezoelectric motor units 14 can be any type of piezoelectric motorunit, which can provide the desired amount of dynamic force in thedesired amount of time. The piezoelectric motors commerciallymanufactured by Nanomotion Ltd. of Haifa, Israel, are suitable.

The operation of a piezoelectric motor is briefly described herein; thedetails of its operation can be found in U.S. Pat. No. 5,616,980 to thecommon assignees of the present invention, the disclosure of which isincorporated by reference.

Four electrodes 16, 17, 18 and 20 are plated or otherwise attached ontothe face (hereinafter “the first face”) of a piezoelectric ceramic 22 toform a checkerboard pattern of rectangles, each substantially coveringone-quarter of the first face. The opposite face (“the second face”) ofthe piezoelectric ceramic 22 is substantially covered with a singleelectrode (not shown). Diagonally located electrodes (17 and 18, 16 and20) are electrically connected by wires 24 and 26 preferably placed nearthe junction of the four electrodes. The electrode on the second face ispreferably grounded.

A relatively hard spacer 28 is attached to a short edge of piezoelectricceramic 22, preferably at the center of the edge.

Piezoelectric ceramic 22 vibrates when electrified. The dimensions ofthe rectangular large face are preferably chosen such that piezoelectricceramic 22 has closely spaced resonance frequencies in an X and a Ydirection (the short and long directions of the rectangular face of thepiezoelectric ceramic 22, respectively), albeit in different modes.Typically, the resonances have overlapping response curves; thus,excitation of the piezoelectric ceramic is achieved by connecting analternating current (AC) voltage at a frequency at which both modes areexcited, to selected ones of the electrodes. When excited, standingwaves at the resonant frequencies are formed in ceramic 22 in both the Xand Y directions.

Piezoelectric ceramic 22 is generally constrained by a pair of fixedsupports 32 and by a pair of resilient supports 34. Supports 34 aretypically formed of rubber. Supports 32 and 34 contact piezoelectricceramic 22 at points of zero movement in the standing wave in the Ydirection. The points of zero movement are along a pair of long edges ofthe ceramic 22. These supports are designed to slide in the Y direction.A resilient support 38 is pressed against the middle of a second shortedge, labeled 40, of ceramic 22, opposite the short edge having spacer28. Support 38 continually supplies pressure (a “preload”) betweenceramic 22 and the body to be moved, such as material 12, which causesthe motion of ceramic 22 to be transmitted to the body to be moved.

It is noted that, when a piezoelectric motor (14A or 14B) is operated,it moves its spacer 28 in both the X and Y directions, where the X and Ydirections are defined, as above, as being along the short and longaxis, respectively, of the piezoelectric motor. The net effect of themovement of the spacer 28 in both X and Y directions, is elliptical, asdescribed hereinbelow with respect to FIG. 2.

In a preferred embodiment of the present invention, piezoelectric motors14A and 14B are electrified in the same direction (shown by arrows 25Aand 25B). That is, both the upper and lower piezoelectric motor units14A and 14B, respectively operate in concert. Thus, both spacers 28A and28B move together alternately, in either the X and Y directions. Thediagonally located electrodes (16 and 20) of upper piezoelectric motor14A, and the opposite diagonally located electrodes (17 and 18) of lowerpiezoelectric motor 14B are electrically connected together.

Reference is now made to FIG. 2 which is an enlarged elevational detailshowing the movement of material 12 in a forward direction 50. Material12 is being pressed by the spacers 28 of both piezoelectric motors 14 atthe same time. That is, material 12 is subject to pressure in a verticalY direction. The combination of this vertical Y pressure and forward Xmovement distorts the material 12 slightly, creating a convex shape, asshown.

The spacers 28 have a two stage cyclical movement., a first stage (amovement period) during which material 12 moves forward and a secondstage during which material 12 does not move. The movement of eachspacer, in both the Y and X directions, can be defined as having apositive aspect, indicated by arrow “+” and a negative aspect, indicatedby arrow “−”. Upper spacer 28A moves forward in a positive X directionwhile it is displaced in a downwards negative Y direction (dashedstructure). At the same time, lower spacer 28B moves forward in apositive X direction but upwards in a positive Y direction (dashedstructure).

During a second stage the spacers move away from material 12 and in the−x direction.(solid line structure). They then move toward the materialand contact the material again and move to the right.

The motion of the upper and lower spacers 28A and 28B is illustrated byarrows 54 and 56 respectively.

In an alternative preferred embodiment of the invention piezoelectricmotors are electrified to transfer motion to material 12 alternatively.While each of the spacers moves in the same manner as the spacers ofFIG. 2, the spacers move “out of phase” such that they alternativelyimpart motion in the +x direction. It might be expected that theflexible material would follow this alternating motion and movetransverse to the x direction, remaining in contact with both spacersand having no net motion in the +x direction. Surprisingly, this doesnot happen. It appears that material 12, even if it is flexible, remainsgenerally in place so that it is alternatively contacted by spacers 28Aand 28B such that it is alternatively moved by the two motors in the +xdirection.

While it is difficult to make measurements of the transverse motion ofmaterial 12, it is possible that the material does move up and downtogether with the motion of the spacers, however, its motion is lessthan that of the spacers such that net motion is provided in the +xdirection.

Reference is now made to FIG. 3 which illustrates a further embodimentof the present invention utilizing a single piezoelectric motor 70 androllers, generally designated 71. First and second rollers 71A and 71Bare situated on opposite sides of material 12. Embodiments havingsimilar elements have similar reference numerals throughout.

First and second rollers 71A and 71B are used in place of the upperpiezoelectric motor 14A of the embodiment of FIG. 1 to provide pressureon material 12. Rollers 71 are any cylindrical type rollers, known inthe art, which are freely rotatable. Pre-loading is provided to thepiezoelectric motor 70 and rollers 71 by pre-loading supports 38, asdescribed hereinabove with respect to the embodiment of FIG. 1.

Piezoelectric motor 70 is distinguished from piezoelectric motors 14,described hereinabove with respect to the embodiment of FIG. 1, byhaving a pair of spacers 72A and 72B attached to short edges 74A and74B, respectively of piezoelectric ceramic 22. Piezoelectric motor 70comprises upper electrodes 76 and 77, adjacent to spacer 72A, and lowerelectrodes 78 and 79 adjacent to spacer 72B. In this embodiment,material 12 is moved around through 180° by the action of piezoelectricmotor 70 on both rollers 71A and 71B.

When piezoelectric motor 70 is operated, both spacers 72A and 72B movesimultaneously in both the X and Y directions. In this case, bothspacers 72A and 72B behave in a manner similar to lower spacer 28B, asdescribed hereinabove with respect to the embodiment of FIG. 1. Spacer72A moves in an upward direction (+y) and in a forward direction (+x) asin the embodiment of FIG. 1.

The net elliptical effect of the movement of spacer 72A causes material12 to be pushed along in the X direction (arrow 50A). Roller 71A whichis in contact with material 12 is rotated in an anti-clockwise directionby the movement of the material 12, as illustrated by arrow 75A.

The lower part of piezoelectric motor 70 is a mirror image of the upperpart. Spacer 72B attached to lower electrodes 78 and 79, acts in asimilar manner to spacer 72A. Thus, the material 12 is also moved alongin a clockwise direction, indicated by arrow 50B. Roller 71B which isrotated in an anti-clockwise direction by the movement of the material12, as illustrated by arrow 75B.

It will be appreciated by persons skilled in the art that thecombination of a single piezoelectric motor 70 have a spacer at eitherend, as described hereinabove can also be used to move two separatelines of material 12. That is, one line of material moves in onedirection indicated by arrow 50A while a second line of material movesin the opposite direction, indicated by arrow 50A.

Reference is now made to FIG. 4 which schematically illustrates afurther embodiment of the present invention in which piezoelectric motor80 is configured to provide differential movement of the material to bemoved. Since this embodiment is identical to the embodiment of FIG. 3,except for the piezoelectric motor unit 80, only this unit is furtherdescribed in detail hereinbelow.

Four electrodes 81, 82, 83 and 84 are plated or otherwise attached ontothe first face of a piezoelectric ceramic 22 to form a checkerboardpattern of rectangles. The opposite face of the piezoelectric ceramic 22is substantially covered with a single electrode (not shown). Diagonallylocated electrodes (81 and 83, 82 and 84) are electrically connected bywires 85 and 86 preferably placed near the junction of the fourelectrodes. The electrode on the second face is preferably grounded.

Adjacent electrodes 81 and 82 have the same dimensions, each electrodehaving a length a Similarly, adjacent electrodes 83 and 84 also have thesame dimensions of a length b, where b is greater than a. Spacers 86Aand 86B are attached to edges of piezoelectric ceramic 22 which areadjacent to pairs of electrodes 81/82 and 83/84 respectively.

Movement in the X direction, indicated by arrow 88, by spacers 86A and86B depends on the length of the electrodes. The material 12 is thusmoved further by spacer 86B than by spacer 86A and is effectively pulledalong. Rollers 71A and 71B rotate in an anti-clockwise direction (arrow75).

Reference is now made to FIG. 5 which schematically illustrates afurther embodiment of the present invention in which a singlepiezoelectric motor 90 and a pair of rollers 71A and 71B are configuredto provide horizontal movement of two separate lengths of materialdesignated 12A and 12B. Since this embodiment is identical to theembodiment of FIG. 3, except for the piezoelectric motor unit 90, onlythis unit is further described in detail hereinbelow.

Piezoelectric motor 90 comprises two longitudinal electrodes 91 and 92which are plated or otherwise attached onto the first face of apiezoelectric ceramic 22, each substantially covering one-half of thefirst face. The opposite face of the piezoelectric ceramic 22 issubstantially covered with a single electrode (not shown) which ispreferably grounded. Spacers 72A and 72B are attached to short edges 74Aand 74B (hidden), respectively of piezoelectric ceramic 22.

In this embodiment, when piezoelectric motor 90 is operated, bothspacers 72A and 72A move simultaneously in both the X and Y directions.However, in contrast to the embodiment of FIG. 3, since electrodes 91and 92 extend longitudinally between spacers 72A and 72B, the netelliptical movement of each spacer causes sheets of material 12A and 12Bto move in the same direction, as illustrated by arrows 94A and 94B,respectively.

During the cycle stage when spacer 72A moves in an upward direction (+y)and in a forward direction (+x), spacer 72B moves in an upward direction(−y) and in a backward direction (−x) and is not in contact withmaterial 12B. Thus, when material 12A is pushed along by the vibrationsinduced by spacer 72A, material 12B is stationary.

During the second part of the cycle, spacer 72B induces material 12B tomove and material 12A is stationary.

It will be appreciated by persons skilled in the art that each oflongitudinal electrodes 91 and 92 may be replaced by two half sizeelectrodes to create the same effect as described hereinabove.

Reference is now made to FIG. 6 which illustrates a yet furtherembodiment of the present invention utilizing three piezoelectric motors14A, 14B and 70, described hereinabove, to move material 12 aroundthrough 180° or to move two separate lines of material in oppositedirections. The upper and lower piezoelectric motors 14A and 14Bcomprise spacers 28A and 28B, respectively, and are similar to thepiezoelectric motors described hereinabove with respect to theembodiment of FIG. 1. Piezoelectric motor 70 comprises a pair of spacers72A and 72B, respectively, and is similar to the piezoelectric motordescribed hereinabove with respect to the embodiment of FIG. 3, and aretherefore not described in any further detail.

Thus, when the three piezoelectric motors 14A, 14B and 70 are operatedtogether, spacers 28A and 72A from piezoelectric motors 14A, and 70,respectively act in a similar manner to spacers 28A and 28B, asdescribed hereinabove with respect to the embodiment of FIG. 1. Thusmaterial 12 moves horizontally in the direction of arrow 50A.

Similarly, spacers 28B and 72B from piezoelectric motors 14B, and 70,respectively also act in a similar manner to spacers 28A and 28B andmaterial 12 moves horizontally in the opposite direction (arrow 50B).

It will be appreciated by persons skilled in the art that the presentinvention is not limited to AS what has been particularly shown anddescribed hereinabove. Rather the scope of the present invention isdefined by the claims which follow:

What is claimed is:
 1. Apparatus for providing linear motion to agenerally flat flexible material, comprising: (a) at least one linearpiezoelectric ceramic motor situated on a first side of the flatflexible material and comprising a piezoelectric vibrator having anexclusive contact surface attached thereto which contacts the flatflexible material and imparts said linear motion and wherein asubstantially same region of the contact surface contacts the materialwhenever the motor imparts motion to the material; and (b) a bearingsurface situated opposite said contact surface on a second side of theflat flexible material, wherein the bearing surface is a contact surfaceof a second piezoelectric motor and wherein the second piezoelectricmotor also imparts said linear motion to the flat flexible material viasaid contact surface of said second piezoelectric motor.
 2. Apparatusaccording to claim 1 wherein the at least one piezoelectric motor andthe second piezoelectric motors both impart linear motion to theflexible material in the same direction.
 3. Apparatus according to claim1 and including a source of electrical energy which applies at least onevoltage to the at least one piezoelectric motor and to the secondpiezoelectric motor such that they impart said linear motion in a givendirection during motion periods which alternate with periods duringwhich said motion is not applied and wherein the motion periods of theat least one piezoelectric motor and the second piezoelectric motor atleast partially overlap.
 4. Apparatus according to claim 3 wherein themotion periods of one of the at least one piezoelectric motor and thesecond piezoelectric motor is fully contained within the motion periodof the other of the one and second piezoelectric motor.
 5. Apparatusaccording to claim 3 wherein the motion periods of the at least onepiezoelectric motor and the second piezoelectric motor substantiallycoincide.
 6. Apparatus according to claim 3 wherein the source ofelectrical energy is operative to cause the contact surfaces of the atleast one piezoelectric motor and second piezoelectric motor to bedisplaced toward the flexible material during their respective periodsof motion such that the material is pinched between the respectivecontact surfaces.
 7. Apparatus according to claim 3 wherein the sourceof electrical energy is operative to cause the contact surface of the atleast one piezoelectric motor to be displaced toward the flexiblematerial during the period of motion of the at least one piezoelectricmotor and to cause the contact surface of the second piezoelectric motorto be displaced away from the flexible material during the period ofmotion of the at least one piezoelectric motor.
 8. Apparatus accordingto claim 7 wherein the source of electrical energy is operative to causethe contact surface of the second piezoelectric motor to be displacedtoward the flexible material during the period of motion of the secondpiezoelectric motor and to cause the contact surface of the at least onepiezoelectric motor to be displaced away from the flexible materialduring the period of motion of the second piezoelectric motor, such thatthe at least one piezoelectric motor and second piezoelectric motoralternately apply motion to the flexible material.
 9. Apparatusaccording to claim 1 wherein the at least one piezoelectric motorcomprises: a second contact surface which contacts and is operative toapply linear motion to a second portion of the flexible material; andfurther comprising: a second bearing surface situated opposite saidsecond contact surface on a second side of the flat flexible material.10. Apparatus for providing linear motion to a generally flat flexiblematerial, comprising: (a) at least one linear piezoelectric ceramicmotor situated on a first side of the flat flexible material and havinga contact surface attached thereto which contacts the flat flexiblematerial and imparts said linear motion and also having a second contactsurface which contacts and is operative to apply linear motion to asecond portion of the flexible material and wherein the linear motionimparted by the contact surface and the second contact surface areanti-parallel; (b) a bearing surface situated opposite said contactsurface on a second side of the flat flexible material; and (c) a secondbearing surface situated opposite said second contact surface on asecond side of the flat flexible material.
 11. Apparatus according toclaim 10 wherein the second bearing surface is a contact surface ofanother piezoelectric motor and wherein the contact surface of the otherpiezoelectric motor also imparts said linear motion to the flat flexiblematerial.
 12. Apparatus according to claim 11 and including a powersupply that applies at least one voltage to the at least onepiezoelectric motor and the other piezoelectric motor such that bothmotors impart linear motion to the flexible material, at the secondportion, in the same direction.
 13. Apparatus according to claim 11wherein the power supply causes the second contact surface of the atleast one piezoelectric motor and the contact surface of the otherpiezoelectric motor to impart said linear motion in a given directionduring further motion periods which alternate with further periodsduring which said motion is not applied and wherein the further motionperiods of the at least one piezoelectric motor and other piezoelectricmotor at least partially overlap.
 14. Apparatus according to claim 13wherein the further motion periods of one of the at least onepiezoelectric motor and the other piezoelectric motor is fully containedwithin the further motion period of the other of the at least onepiezoelectric motor and the other piezoelectric motor.
 15. Apparatusaccording to claim 14 wherein the further motion periods of the at leastone piezoelectric motor and the other piezoelectric motor coincide. 16.Apparatus according to claim 13 wherein the power supply causes thesecond contact surface of the at least one piezoelectric motor and thecontact surface of the other piezoelectric motor to be displaced towardthe flexible material during their respective further periods of motionsuch that the material is pinched between the respective contactsurfaces.
 17. Apparatus according to claim 11 wherein the power supplycauses the second contact surface of the at least one piezoelectricmotor to be displaced toward the flexible material during the furtherperiod of motion of the at least one piezoelectric motor and causes thecontact surface of the other piezoelectric motor to be displaced awayfrom the flexible material during the further period of motion of the atleast one piezoelectric motor.
 18. Apparatus according to claim 17wherein the power supply causes the contact surface of the at otherpiezoelectric motor to be displaced toward the flexible material duringthe period of motion of the other piezoelectric motor and causes thesecond contact surface of the at least one piezoelectric motor to bedisplaced away from the flexible material during the period of motion ofthe other piezoelectric motor such that the at least one piezoelectricmotor and other piezoelectric motor alternately apply motion to theflexible material.
 19. Apparatus according to claim 10 wherein thesecond bearing surface is the surface of a roller.
 20. Apparatusaccording to claim 1 wherein the material is paper.
 21. Apparatusaccording to claim 1 wherein the material is cloth.
 22. A method forproviding linear motion to a generally flat flexible material,comprising: (a) contacting a contact surface of at least one linearpiezoelectric ceramic motor with a first side of the flat flexiblematerial, said contact surface being attached to a single piezoelectricvibrator comprised in the linear motor so that the surface impartslinear motion to portions of the material which are in contact therewithand wherein a substantially same region of the contact surface contactsthe material whenever the motor imparts motion to the material; and (b)providing a bearing surface situated opposite said contact surface on asecond side of the flat flexible material, wherein the bearing surfaceis a contact surface of a second linear piezoelectric motor and whereinthe second piezoelectric motor also imparts said linear motion to theflat flexible material.
 23. A method according to claim 22 wherein theat least one piezoelectric motor and the second piezoelectric motor bothimpart linear motion to the flexible material in the same direction. 24.A method according to claim 23 wherein the piezoelectric motors impartsaid linear motion in a given direction during motion periods whichalternate with periods during which said motion is not applied andwherein the motion periods of the at least one piezoelectric and secondpiezoelectric motor at least partially overlap.
 25. A method accordingto claim 24 wherein the motion periods of one of the at least onepiezoelectric and the second piezoelectric motor is fully containedwithin the motion period of the other piezoelectric motor.
 26. A methodaccording to claim 24 wherein the motion periods of the at least onepiezoelectric and second piezoelectric motors coincide.
 27. A methodaccording to claim 23 and including displacing the contact surfaces ofthe at least one piezoelectric motor and second piezoelectric motortoward the flexible material during their respective periods of motionsuch that the material is pinched between the respective contactsurfaces.
 28. A method according to claims 23 wherein the contactsurface of the at least one piezoelectric motor is displaced toward theflexible material during the period of motion of the at least onepiezoelectric motor and wherein the contact surface of the secondpiezoelectric motor is displaced away from the flexible material duringthe period of motion of the at least one piezoelectric motor.
 29. Amethod according to claim 28 wherein the contact surface of the secondpiezoelectric motor is displaced toward the flexible material during theperiod of motion of the second piezoelectric motor and wherein thecontact surface of the at least one piezoelectric motor is displacedaway from the flexible material during the period of motion of thesecond piezoelectric motor, such that the at least one piezoelectricmotor and second piezoelectric motor alternately apply motion to theflexible material.
 30. A method according to claim 22 and including: (a)contacting a second contact surface of the at least one ceramicpiezoelectric motor with one side of the flat flexible material, saidmotor being operative to impart linear motion to a second portion of thematerial which is in contact with the second contact surface; and (b)providing a second bearing surface situated opposite said contactsurface on another side of the flat flexible material.
 31. A method forproviding linear motion to a generally flat flexible material,comprising: (a) contacting a contact surface of at least one linearpiezoelectric ceramic motor with a first side of the flat flexiblematerial, said contact surface being attached to the linear motor suchthat the surface imparts linear motion to portions of the material whichare in contact therewith; and (b) providing a bearing surface situatedopposite said contact surface on a second side of the flat flexiblematerial; (c) contacting a second contact surface of the at least oneceramic piezoelectric motor with one side of the flat flexible material,said motor being operative to impart linear motion to a second portionof the material which is in contact with the second contact surface andwherein the linear motion imparted by the contact surface and the secondcontact surface are anti-parallel; and (d) providing a second bearingsurface situated opposite said second contact surface on another side ofthe flat flexible material.
 32. A method according to claim 31 whereinthe second bearing surface is a contact surface of another piezoelectricmotor and wherein the contact surface of the other piezoelectric motoralso imparts said linear motion to the flat flexible material.
 33. Amethod according to claim 32 wherein the at least one piezoelectricmotor and the other piezoelectric motor both impart linear motion to theflexible material, at the second portion, in the same direction.
 34. Amethod according to claim 32 wherein the second contact surface of theat least one piezoelectric motor and the contact surface of the otherpiezoelectric motor impart said linear motion in a given directionduring further motion periods which alternate with further periodsduring which said motion is not applied and wherein the further motionperiods of the at least one piezoelectric motor and other piezoelectricmotors at least partially overlap.
 35. A method according to claim 34wherein the further motion periods of one of the at least onepiezoelectric motor and the other piezoelectric motor is fully containedwithin the further motion period of the other of the at least one andother piezoelectric motors.
 36. A method according to claim 35 whereinthe further motion periods of the at least one piezoelectric and theother piezoelectric motor coincide.
 37. A method according to claim 34wherein the second contact surface of the at least one piezoelectricmotor and the contact surface of the other piezoelectric motor aredisplaced toward the flexible material during their respective furtherperiods of motion such that the material is pinched between therespective contact surfaces.
 38. A method according to claim 33 whereinthe second contact surface of the at least one piezoelectric motor isdisplaced toward the flexible material during the further period ofmotion of the at least one piezoelectric motor and wherein the contactsurface of the other piezoelectric motor is displaced away from theflexible material during the further period of motion of the at leastone piezoelectric motor.
 39. Apparatus according to claim 38 wherein thecontact surfaces of the other piezoelectric motor is displaced towardthe flexible material during the period of motion of the otherpiezoelectric motor and wherein the contact surface of the at least onepiezoelectric motor is displaced away from the flexible material duringthe period of motion of the other piezoelectric motor such that the atleast one piezoelectric motor and other piezoelectric motor alternatelyapply motion to the flexible material.
 40. A method according to claim31 wherein the second bearing surface is the surface of a roller.
 41. Amethod according to claim 22 wherein the material is paper.
 42. A methodaccording to claim 22 wherein the material is cloth.